I ran my wires the same way everyone else did, but I pulled the dash panel off and tapped into the headlight switch for a +12v, a dimmed 12v, and a GND line. Different color wires are used on different year trucks with different style headlight switches, so make sure you reference an appropriate shop manual.
I ran three wires up into the A-pillar from the headlight switch, then tapped into each of those three as many times as I needed for the power to each gauge. That saved me from having to tap into OEM harness in more than one point per wire. Worked really well.
Tim